[Intel-gfx] [PATCH 3/3] drm/i915: optimise intel_runtime_pm_{get, put}

[David Weinehall]

Benchmarking shows that on resume we spend quite a bit of time
just taking and dropping these references, leaving us two options;
either rewriting the code not to take these references more than
once, which would be a rather invasive change since the involved
functions are used from other places, or to optimise
intel_runtime_pm_{get,put}().  This patch does the latter.
Initial benchmarking indicate improvements of a couple
of milliseconds on resume.

Original patch by Chris, with slight fixes by me.

Signed-off-by: David Weinehall <david.weineh...@linux.intel.com>
CC: Chris Wilson <ch...@chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/intel_runtime_pm.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/drivers/gpu/drm/i915/intel_runtime_pm.c 
b/drivers/gpu/drm/i915/intel_runtime_pm.c
index 356c662ad453..4bf279023b39 100644
--- a/drivers/gpu/drm/i915/intel_runtime_pm.c
+++ b/drivers/gpu/drm/i915/intel_runtime_pm.c
@@ -2632,6 +2632,9 @@ void intel_runtime_pm_get(struct drm_i915_private 
*dev_priv)
        struct pci_dev *pdev = dev_priv->drm.pdev;
        struct device *kdev = &pdev->dev;
 
+       if (atomic_inc_not_zero(&dev_priv->pm.wakeref_count))
+               return;
+
        pm_runtime_get_sync(kdev);
 
        atomic_inc(&dev_priv->pm.wakeref_count);
@@ -2653,6 +2656,9 @@ bool intel_runtime_pm_get_if_in_use(struct 
drm_i915_private *dev_priv)
        struct pci_dev *pdev = dev_priv->drm.pdev;
        struct device *kdev = &pdev->dev;
 
+       if (atomic_inc_not_zero(&dev_priv->pm.wakeref_count))
+               return;
+
        if (IS_ENABLED(CONFIG_PM)) {
                int ret = pm_runtime_get_if_in_use(kdev);
 
@@ -2695,6 +2701,9 @@ void intel_runtime_pm_get_noresume(struct 
drm_i915_private *dev_priv)
        struct pci_dev *pdev = dev_priv->drm.pdev;
        struct device *kdev = &pdev->dev;
 
+       if (atomic_inc_not_zero(&dev_priv->pm.wakeref_count))
+               return;
+
        assert_rpm_wakelock_held(dev_priv);
        pm_runtime_get_noresume(kdev);
 
@@ -2714,6 +2723,9 @@ void intel_runtime_pm_put(struct drm_i915_private 
*dev_priv)
        struct pci_dev *pdev = dev_priv->drm.pdev;
        struct device *kdev = &pdev->dev;
 
+       if (!atomic_dec_and_test(&dev_priv->pm.wakeref_count))
+               return;
+
        assert_rpm_wakelock_held(dev_priv);
        atomic_dec(&dev_priv->pm.wakeref_count);
 
-- 
2.10.2

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